MIEX® Treatment of an Effluent-Impacted Stream

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Publication Date


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Journal of the American Water Works Association






American Water Works Association


A case study was conducted to examine the magnetic ion exchange (MIEX®) process for treating water impacted by wastewater treatment plant effluent and removing disinfection by-product precursors. The plant effluent increased dissolved organic carbon, ultraviolet absorbance at 254 nm (UV254), anions, and disinfection by-product precursors at the discharge and downstream locations. The MIEX process reduced dissolved organic carbon by 42-47%, UV254 absorbance by 61-68%, and trihalomethane and haloacetic acid formation potential (FP) by 50-70% at different downstream locations. On the other hand, halonitromethane FP was reduced by only 10-15% and N-nitrosodimethylamine (NDMA) FP increased as a result of chloramination after MIEX treatment. Uniform formation condition experiments showed that NDMA concentrations remained below 10 ng/L when chlorine alone or 40 min of chlorine contact time before ammonia addition were used for postdisinfection. However, use of preformed chloramine resulted in 36 ng/L of NDMA formation. Because MIEX substantially removes trihalomethane and haloacetic acid precursors, it may allow the use of more chlorine for longer contact time, which can lead to less NDMA formation.